Electron beam-tuning-indication tube



Feb. 4, 1958 H. E. J. H. STIETZEL E L 2,822,494

, ELECTRON BEAM-TUNING-INDICATION TUBE 2 sheets-sheet 1 Filed Nov. 13.1952 INVENTORS Alexander Hons Adolf Siebenberg -Horsf Edgclr JohnHeinyich Srietzel 1958 H. E. J. H. STIETZEL ET AL 2,822,494

ELECTRON BEAM-TUNING-INDICATION TUBE Filed Nov. 13, 1952 2 Sheets-Sheet2 IN VEN TORS Al'exonder Hons Adolf Siebefiberg Horst Edgor JohnHeinrich Stiefzel AGENT ELECTRON BEAM-TUNING-INDICATION TUBE Horst EdgarJohn Heinrich Stietzel, Hamburg, and Alexander Hans Adolf Siebenberg,Hamburg-Fuhlshuttel, Germany, assignors, by mesne assignments, to NorthAmerican Philips Company, Inc., New York, N. Y., a corporation ofDelaware Application November 13, 1952, Serial No. 320,166 Claimspriority, application Germany March 20, 1952 7 Claims. (Cl. SIS-107.5)

The invention relates to a cathode-ray tube for tuning indication,having shadow angles or the like controlled by deflection rods and, ifdesired, an amplifying system housed in the same bulb.

Such tuning indicators have been known for a long time and efiorts havebeen made to construct these tubes in order to obtain an optimumdistinctness of indication or an optimum sensitivity, in a manner suchthat in the event of complete control they produce a maximum shadowangle.

For this purpose it has been suggested to provide a counter-electrode orcounter-electrodes, preferably being at the potential of the luminescentscreen, in the proximity of the cathode in a manner such that a strongand extensive field is produced between the cathode and thecounter-electrode and between the deflection electrode andcounter-electrode.

This construction has a limitation in that these counterelectrodesthemselves project shadow sectors onto the screen, these sectors havinga constant width, so that the useful screen surface is reduced. Efiortshave been made to obviate this limitation by arranging the cathode withthe associated electrodes eccentrically within the tube or to theluminescent screen. Thus, however, the second shadow sector produced inthe case of concentrical arrangement is lost; this sector contributedefiectively to enhance the tuning indication. Moreover, also forstructural reasons this arrangement is not very favourable.

The invention obviates this disadvantage and consists in that theequipotential lines of the electric field between the screen and thecathode are made substantialy elliptical in form by a shaping of theparts of the system at the potential of the screen, without introducingadditional electrodes.

An efiicient embodiment of the tuning indicator according to theinvention consists in that the elliptical shape of the equipotentiallines is obtained by means of a rotational-unsymmetrical shape of thescreen, the circumference of which varies periodically. In other words,the shape of the screen is not a surface of revolution.

It is advisable to use a funnel-shaped luminescent screen, thecross-sectional area of which is oval and which has angles of differentslopes, which are flatter in the direction of the long axis, on whichthe deflection rods are also located, and which extend more steeply inthe direction of the short axis.

A further advantageous embodiment consists in that the funnel-shapedluminescent screen is substantially circular and has lines ofinclination which extend with uniform steepness in the direction throughthe control-rods and extend first flatly towards the inside thengradually more steeply in the direction at right angles thereto. In thiscase, however, the light distribution of the luminescent surface maylack uniformity.

This is avoided, if the funnel-shaped screen has a circuralcross-sectional area and lines of inclination which extend first steeplytowards the inner side in the direction through the control-rods andthen extend gradually more flatly, but exhibit a constant slope in thedirection at right angles thereto.

The elliptical shape of the equipotential lines may be obtained not onlyby a corresponding shape of the luminescent screen, but also by suitableshape of the cathode hood, which has to screen principally the lightemanating from the incandescent cathode and is usually at the potentialof the screen. As an alternative, these two measures may be combined, sothat they support one another. To this end, it is desirable to shape thecathode hood, which is at the potential of the screen, in the form of acup having a short, substantially cylindrical wall,

which is provided with recesses at the areas near the the plan view ofthree embodiment of a luminescent screen of a tube according to theinvention.

Fig. 8 shows a cathode hood having recesses in accordance with theinvention.

Figs. 1 and 2 show the equipotential lines of the electric field betweenthe cathode 2, which is surrounded by a grid 1, and the luminescentscreen 3 in a tuning indicator of conventional construction; thecontrol-rods are designated by 4. If the control-rods are, at cathodepotential, the form of the equipotential lines is that shown in Fig. 1.If the rods are substantially at the potential of the luminescentscreen, the shape of the equipotential lines shown in Fig. 2 isobtained. The electrons emanating from the cathode 2 first follow thelines at right angles to the equipotential lines and then extendstraight on.

In this way are produced the boundaries of the shadow sectors shown indotted lines in Figs. 1 and 2. The same is shown in Figs. 3 and. 4 foran indicator tube according to the invention; the same referencenumerals are used in these figures. It is assumed in the first placethat the equipotential lines have the elliptical shape shown in Fig. 3when the control-rods 4 are at cathode potential, though the means forobtaining this form are not shown. The deformation of the equipotentiallines for the case in which the control-electrodes 4 are substantiallyat the potential of the luminescent screen is shown in Fig. 4. Acomparison between Figs. 1 and 3 shows that, owing to the ellipticalshape of the equipotential lines, a materially larger shadow angle isobtained.

In order to obtain such elliptical equipotential lines, use may be madeof a luminescent screen as shown in Fig. 5. As is shown, the upper widerportion of the luminescent screen 3 is oval in shape, the aperture atthe bottom of this funnel-shaped screen being, as usual, circular. Inthis aperture are shown the two control-rods 4, the cathode 2 being, ofcourse, at the center and coaxially within the screen 3. The associatedlateral views, below and to the right of the plan view, show that theangles of inclination of this funnel have different steepnesses; theyare flatter in the direction of the long axis of the ellipse, andsteeper in the direction of the short axis. The lateral views shown arealmost identical to cross-sectional views through the screen along themajor and minor axes of the oval screen 3. These cross-sectional viewswould correspond to the intersections of the screen with orthogonalplanes having the screen axis as their line of intersection. As will benoted, these two intersections, i. e., the side views shown in thedrawing,

. Patented eb. 4,

are different, which means that the screen 3 is not a sur- M face ofrevolution.

A further embodiment of such a luminescent screen is shown in Fig. 6.The luminescent screen 3 is, in this case, circular, so that thespectator observes the conventional circular shape and, moreover, thecircular sectional area of the bulb is satisfactorily utilized. in orderto obtain in this case an elliptical field of equipotential lines, theangles of inclination of the funnel are slightly shortened in thedirection of the axis x--x, as is evident from the associated later orside view. That is, these side portions of the screen are concaveinstead of straight. In the direction of the axis y-y the angle ofinclination is straight, as is evident from the associated lateral view.With respect to the profile of inclination, a uniform transition existsbetween these two axes.

A further possible shape of the luminescent screen is shown in Fig. 7.Here again the screen is circular, but the lines of inclination arestraight in the direction of the axis x-x, and in the direction of theaxis y-y, the steepness varies in a sense contrary to that of theembodiment described in Fig. 6. That is, the side portions are convexinstead of concave. The shape of the lines of inclination is evidentfrom the associated lateral views.

According to the invention, an elliptical field is obtainable by usingluminescent screens having the common feature that use is made ofrotational-unsymmetrical bodies. However, the cathode hood, whichprimarily serves to screen the light emanating from the cathode, mayalso be utilized to obtain an electric field of this shape. This hoodusually is at the potential of the luminescent screen, and, since incomparison with the conventional electrode system, this hood hasappreciable dimensions, it exerts a marked influence on the shape of theelectric field. A suitable embodiment of such a hood is shown in Fig. 8.This hood comprises a cylindrical Wall 5 of comparatively small height,closed at the top by a slightly arcuate bottom 6 and supported by staywires 7. The lower edge of the wall 5 is provided with recesses 8 at twoareas diametrically opposite one another; these recesses produce anelliptical deformation of the electric field. It is advantageous to usea cathode hood as shown in Fig. 8 in conjunction with a luminescentscreen as shown in any of the preceding embodiments, in order to havethe effects of the two parts support one another.

As indicated earlier, the difierent cross-sectional views of the screen,made by the orthogonal planes, indicate a screen construction thatdistorts what was primarily a field with circular equipotential lines toone with mainly elliptical equipotential lines, which, as illustrated inFigs. 3 and 4, results in a wider shadow region with the minimum signal.

What we claim is:

1. A cathode-ray tuning indicator tube comprising a hollow, luminescentscreen, a cathode arranged centrally and coaxially within theluminescent screen, and means including deflection members disposedbetween the cathode and screen for controlling, by its potential, theextent of fluorescence of the screen and arranged to provide two opposedfluorescent areas on the screen, the intersections of orthogonal planes,having the axis of the screen as their line of intersection, with thescreen being different, whereby said screen has a shape different from asurface of revolution and'the equipotential lines of the electric fieldt cross-section with a long axis in one direction and a short axis atright angles thereto, a cathode arranged centrally and coaxially withinthe luminescent screen, and means including deflection members disposedalong the long axis of the oval and between the cathode and screen forcontrolling, by its potential, the extent of fluorescence of the screenand arranged to provide two opposed fluorescent areas on the screen, theintersections of orthogonal planes, having the axis of the screen astheir line of intersection, with the screen being different, wherebysaid screen has a shape ditterent from a surface of revolution and theequipotential lines of the electric field established between cathodeand screen when a potential differenceis applied therebetween arestronglyelliptical in shape.

4. A cathode-ray tuning indicator tube comprising a funnel-like, hollow,luminescent screen, a cathode arranged centrally and coaxially withinthe luminescent screen, and means including deflection members disposedbetween the cathode and screen for controlling, by its potential, theextent of fluorescence of the screen and arranged to provide two opposedfluorescent areas on the screen, said funnel-like screen having concaveportions on opposed side Walls so that the intersections of orthogonalplanes, having the axis of the screen as their line of intersection,with the screen are different, whereby said screen has a shape difierentfrom a surface of revolution and the equipotential lines of the electricfield established between cathode and screen when a potential differenceis applied therebetween are strongly elliptical in shape.

5. A cathode-ray tuning indicator tube comprising a funnellike, hollow,luminescent screen, a cathode arranged centrally and coaxially withinthe luminescent screen, and means including deflection members disposedbetween the cathode and screen for controlling, by its potential, theextent of fluorescence of the screen and arranged to provide two opposedfluorescent areas on the screen, said funnel-like screen having convexportions on opposed side walls so that the intersections or orthogonalplanes, having the axis of the screen as their line of intersection,with the screen are different, whereby said screen has a shape ditferentfrom a surface of revolution and the equipotential lines of the electricfield established between cathode and screen when a potential differenceis applied therebetween are strongly elliptical in shape.

References Cited in the tile of this patent UNITED STATES PATENTS mm....W

